‘None of this sir business, please. I’m Robert, remember?’

‘Yes, s . . .’ He found it impossible to envisage ever being comfortable enough to call this man by his first name.

‘If you’ve finished your tea, perhaps you would like to come to my office so that I can fill you in on our work here?’

‘Good luck, old boy. See you on the other side,’ someone whispered.

Robert Watson-Watt’s office was perhaps the most opulent Vic had ever seen, thickly carpeted with walls lined in gold-embossed leather above panels of oak carved in an ornate linen-fold pattern. Through stone-mullioned windows was the same astonishing view he’d admired from the terrace. On the table between two leather sofas sat a tray with the remains of tea, including a large slice of fruit cake and a couple of Garibaldi biscuits.

‘Take a seat, old chap, and do help yourself. Never could stand the biscuits, not since someone told me the raisins were squashed flies, but I’m told they’re perfectly edible. And the cake is pretty good.’

Vic demurred, then weakened. ‘It’s been a long time since breakfast, s . . .’

Robert Watson-Watt arranged himself comfortably on the opposite sofa, stretching out his legs and leaning back, hands linked behind his head and elbows akimbo. It was a pose that conveyed ultimate confidence without any need for assertion, and Vic wondered whether he would ever achieve such a state of self-assuredness.

‘Go for it, lad. Keep the wolf from the door till supper. Now, I suppose you’ll be wanting to know what you’ve let yourself in for?’

With his mouth full of cake, Vic could only nod.

‘Well, it all started when the Air Ministry asked us to develop a death ray. Something that would kill a sheep at a hundred yards, that was their criterion.’

Vic swallowed. ‘Surely that would require so much power . . .?’

‘Just so. We managed to persuade them the idea was completely bonkers, because you’d need to cart around a ruddy great power station just to stun the poor animal. But a colleague suggested that radio waves might prove useful in other ways.’

He paused again, peering over his spectacles, his eyebrows raised. Vic was familiar with the expression, the very same that his physics teachers used to adopt.

‘For shipping, sir?’

‘Of course, of course,’ Watson-Watt jumped in with a hint of impatience. Failed that test, then, Vic thought to himself. ‘They’ve been doing that to detect icebergs ever since the Titanic went down. But what we’re doing is different, you see, which is why we have to keep it so ruddy secret. If we can perfect this thing, we’ll get Hitler on the back foot.’

He leapt up and began to pace, as though unable to contain his energy.

‘This thing, sir?’ Vic prompted, after a few moments.

‘The thing is, Mackensie – is it okay if I call you that?’